1. Field of the Invention
The present invention relates to a true union ball valve and, more particularly, to a true union ball valve having simplified means for interlocking the internal parts thereof.
2. Description of the Prior Art
Commercial and industrial PVC pipe systems often include two position, on/off ball valves for controlling the flow of fluid through the individual pipes of the system. A typical ball valve includes a body having a continuous axial chamber and a rotatable ball in the center of the chamber, the ball having a hole therethrough which, in one position thereof, is aligned with the axial chamber, permitting fluid flow through the valve, and which, in another position thereof, is perpendicular to the chamber so that the ball blocks all flow through the valve. The ball is connected to a stem which extends laterally through the body and is connected to a handle for manipulation thereof. The ball valve includes a variety of other internal valve parts which function to lock the ball within the chamber and to seal the valve components to prevent leakage of fluid from the system.
A preferred type of ball valve is commonly referred to as a "true union" valve. When a true union valve is connected between two ridged pipes of a pipe system, the valve may be removed from between the pipes as an assembled unit or cartridge without retraction of the pipes. This permits the valve to be removed, repaired, or replaced, simply and efficiently, without disassembling the entire pipe system.
While several different true union ball valves have been developed, a number of problems exist therewith. A typical true union ball valve, in addition to including a body having a rotatable ball in the chamber therein, includes a seal carrier on each side of the ball, the seal carrier supporting a ball seal, a body seal, and a flange seal to fully seal the valve and prevent fluid loss therefrom. A flanged socket is connectable to the adjacent ends of a pipe system and the valve is positionable between the sockets, with the flanges thereof engaging the ends of the seal carriers and/or the ends of the valve body. A flanged nut which is axially movable along the pipes engages external threads on the valve body to connect each socket to the body.
It is desirable to provide means for locking the seal carriers to the body so that the valve will operate and stay closed even if only one end is connected to a pipe. The most common technique for achieving this is to make one of the seal carriers integral with the body and to insert the remaining valve elements through the other end of the body. The problem with this arrangement is that only one end of the valve may be disconnected from a piping system and the internal parts of the valve are not interchangeable. Such a valve, by being unsymmetrical, is also relatively inexpensive to manufacture.
Another alternative is to lock the seal carriers to the body by providing internal threads in the ends of the body and external threads on the seal carriers so that the seal carriers may be screwed into the ends of the valve body. Such valves are expensive to manufacture and require special tools to engage the seal carriers to remove them from the valve body.
Still another alternative is to provide the valve body and the seal carrier with a bayonet-type connection so that the seal carriers may be freely inserted into the ends of the valve body and then rotated through a given angle to lock the carriers relative to the body. While this is a substantial improvement over the use of threads, the resultant valve is complex to manufacture and the finished product is relatively expensive.